Cardiac arrest is a life-threatening medical condition that may be treated with external defibrillation. External defibrillation includes applying electrodes to a patient's chest and delivering an electric shock to the patient to depolarize the patient's heart and restore normal sinus rhythm. The chances that a patient's heart can be successfully defibrillated increase significantly if a defibrillation pulse is applied quickly.
In some cases, the patient's need is urgent and the patient cannot wait for trained personnel, such as paramedics, emergency medical technicians, or others trained in defibrillations techniques, to arrive. In recognition of the need for prompt treatment and the advantages of early defibrillation, automated external defibrillators (AEDs) are becoming more commonplace, and are available in venues such as airports, health clubs and auditoriums.
When an AED is used to treat a patient, much of the treatment is performed by the AED rather than the person who operates the AED. In general, the AED automatically measures the patient's cardiac signals, assesses whether a shock is indicated and charges a storage element in preparation for giving the shock. When a shock is indicated, the AED may cue the operator to administer the shock, or the AED may administer the shock automatically. In addition, many AEDs include visual displays, voice instructions and other audible messages that tell the operator about the status of the defibrillator. By delivering therapy in advance of arrival of emergency personnel, an AED can save a patient's life.